My 2013 Tesla Model S, when new, had an EPA range of 265 miles. But six or eight years down the road, with 100,000-plus miles on the odometer, there’s no way to know what my range will be.

It’s an especially worrisome question for Model S owners, for two reasons:

First, the list price of a replacement 85-kWh battery pack is a whopping $44,000. (That cost would presumably be reduced by the trade-in value of the old pack, a number that has not been publicly revealed as far as I know.)

By contrast, a Nissan Leaf replacement battery costs $5,500, after the trade-in allowance.

Second, it’s a little-noticed fact that Tesla’s eight-year “infinite-mile” battery-pack warranty doesn’t actually guarantee any particular level of capacity. It only guarantees that the battery will work properly to propel the car.

In the wake of more-rapid-than-expected battery capacity losses in Leafs in hot weather, Nissan now guarantees that the Leaf battery will retain at least 70 percent capacity after five years and/or 60,000 miles.

Nissan is the only company to guarantee long-term battery capacity.

Reason for optimism

Only time will tell, of course, what the rate of battery degradation and range loss will be for electric cars currently on the road.

Range losses for its two-seat predecessor, the Tesla Roadster, have proven to be less than expected since it was introduced in 2008.

And a recent unofficial study by a Dutch engineering professor shows an average range loss for the Model S even less than the Roadster’s. (Not surprising; the Model S battery management system is more sophisticated than the Roadster’s.)

Roadster data

When Tesla first introduced the Roadster in 2008, it predicted that the battery pack would retain at least 70 percent of its capacity after five years and 50,000 miles of driving.

The recent Model S numbers from The Netherlands are even more encouraging.

Based on 84 data points from the 85-kWh version of the Model S and six from 60-kWh cars, the study concludes that the Model S will retain about 94 percent of its capacity after 50,000 miles, with losses thereafter shrinking to about 1 percent per 30,000 miles.

That means that after 100,000 miles, the typical Model S is projected to retain about 92 percent of its battery capacity and range.